1. Field of the Invention
This invention relates to the preparation of organic carbonates. More particularly it relates to ligands for the preparation of dimethyl carbonate (DMC). DMC may be used as a gasoline extender and octane enhancer, as an organic solvent, or as a reactant in place of phosgene in the preparation of isocyanates, polycarbonates, and various agricultural and pharmaceutical intermediates.
Dimethyl carbonate (DMC) may be prepared by the reaction of methanol with carbon monoxide and oxygen in the presence of a catalyst system. Those skilled in the art, constantly seek new or improved catalysts or ligands for such catalysts to lower costs, to improve reaction conditions, yield and rate of production, and to facilitate separation of reactants, products, and catalysts.
Thus, it is an object of this invention to provide an improved method of preparing dimethyl carbonate, lower the cost of the process, substantially increase the yield and rate of production of dimethyl carbonate, and ease the separation of DMC and water from the catalyst system.
2. Disclosure Statement
U.S. Pat. No. 3,114,762 discloses as catalysts metal salts including chlorides and bromides of platinum and palladium plus an oxidizing agent such as iron or copper salts having the same anion.
U.S. Pat. No. 3,227,740 discloses as catalyst mercuric halides or carboxylates.
Saegusa et al, J. Org Chem., 35, 2976-2978 (1970) discloses the reaction of CO with copper alkoxides including the dimethoxide, the diallyloxide, the chloride methoxide, and the acetylacetonate methoxide.
Romano et al IEC Prod. Res. Dev. 19, 396-403 (1980) discloses as catalyst cuprous chloride/cupric chloride methoxide.
U.S. Pat. No. 4,218,391 discloses as catalysts salts of metals of Group IB, IIB, and VIII, preferably monovalent copper such as cuprous bromide, chloride, or perchlorate.
U.S. Pat. No. 4,318,862 discloses as catalyst salts of metals of Groups IB, IIB, or VIII, typically a copper salt such as CuCl.
U.S. Pat. No. 3,846,468 discloses as catalysts cuprous chloride complexes with various organic compounds such as pyridine, dipyridyl, imidazole, phenanthroline, alkyl, or aryl phosphines, dimethyl sulfoxide, dimethyl formamide, quinuclidine, acetonitrile, benzonitrile, malonitrile, succinodinitrile, or adiponitrile.
U.S. Pat. No. 3,980,690 discloses as catalyst a complex of copper chloride and poly-4-vinylpyridine.
Rivetti et al, J. Organometallic Chem, 174 (1979) 221-226 discloses as catalysts palladium (II) complexes in the presence of ligands and added bases. Alkyl phosphines are said to inhibit carbonylation almost completely. The presence of tertiary amines enhances the formation of dimethyl carbonate. Low yields (6% or less) of dimethyl carbonate are obtained with Pd(OAc).sub.2 in the presence of ligands such as R.sub.3 P where R is p-C.sub.6 H.sub.4 OCH.sub.3. Yield is increased to 61% in the presence of a base such as diisopropylethylamine.
U.S. Pat. No. 3,952,045 discloses as catalysts organic phosphorus compounds such as phosphine oxide, phosphite, phosphate, or phosphonate plus copper halides.
U.S. Pat. No. 4,360,477 dicloses as catalysts cupric halides inter alia.
Yang et al CA 86, 17186u (1977) discloses as catalysts PdCl.sub.2, CuCl.sub.2, MnCl.sub.2, and LiCl.
Lapidus et al CA 93, 72338j (1980) discloses as catalyst MnCl.sub.2, KMnO.sub.4, CuCl.sub.2, LiCl, and Mn(OAc).sub.3.
Itatani, Japanese patent publication No. 54-24827 pub 24 Feb. 1979 discloses as catalyst a cuprous halide plus as auxiliary catalyst a halide of an alkali metal or an alkaline earth metal.
U.S. Pat. No. 4,370,275 discloses as catalyst compositions containing copper, chemically bonded oxygen, and halogen and a nitrogen base. A typical catalyst contains CuO or Cu(OCl).sub.2 and n-butylamine inter alia. Preferred combinations include: CuCO.sub.3, Cu(OH).sub.2 ; CuCl.sub.2 and pyridine hydrochloride etc.
U.S. Pat. No, 4,131,521 discloses an electrochemical process utilizing a non-fluoride halide-containing electrolyte.
U.S. Pat. No. 4,113,762 discloses as catalyst a complex of copper (as CuCl) with VCl.sub.3, CrCl.sub.3, FeCl.sub.3, CoCl.sub.2, AlCl.sub.3, or SiCl.sub.4.
U.S. Pat. No. 4,361,519 discloses as catalyst (i) a Bronsted base such as a quaternary ammonium, phosphonium, or sulfonium compound or an alkoxide or hydroxide of alkali metal or alkaline earth metal or a salt of a strong base and a weak acid or amines etc. plus (ii) a Group VIII B element Ru, Rh, Pd, Os, Ir or Pt plus (iii) oxygen plus (iv) a redox catalyst such as a Mn or Co containing catalyst. A typical system includes (i) a pentamethylpiperidine, (ii) PdBr.sub.2 and (iii) pyridine adduct of salicylaldehyde-ethylene diamine Co (II) complex.
European Pat. No. 0,071,286 discloses as catalyst a copper compound such as a halide (in the presence of an amine) plus a sulphone such as dimethyl sulphone or sulfolane.